Absolute encoders are known for providing an output indication of the position of a sensing head relative to a measuring scale. For sensing rotary displacement, the scale is in the form of a disc rotating a plurality of concentric tracks which provide respective bits of a multi-bit digital code. For linear rotation sensing, the scale is an elongated scale member containing linearly arranged parallel code tracks. The rotary code tracks are sensed by an array of sensors each concentric with a respective track to provide an output signal representing a bit of the multi-bit output code. The code tracks are often formed of optically responsive segments, which segments are light transmissive or light reflective, but the tracks can alternatively be of other forms such as magnetic, capacitive or inductive. Higher resolution is achieved by increasing the number of code tracks to provide a higher number of bits in the output code.